The present invention relates to a beam direction module using mirrors to control directions of light beams and optical switch using the same.
In optical communication using optical fibers, there can be used an N-by-N optical switch, that is, an apparatus which has N input ports and N output ports and in which connection between the N input ports and the N output ports can be switched so that any one of optical signals sent to the N input ports through optical fibers can be connected to one of the N output ports.
In a general configuration of a switch called “three-dimensional optical matrix switch”, a collimator array having collimators arranged in the form of an array for converting optical signals into light beams and outputting the light beams to a space and a micro-mirror array generally produced by a micro electro-mechanical system (MEMS) technique and having movable micro-mirrors arranged in the form of an array are paired with each other and disposed on each of input and output sides. The direction of a beam emitted from one of the collimators on the input side is controlled by two micro-mirrors so that the beam is led to any one of the collimators on the output side.
U.S. Pat. No. 6,504,967 has made description about an optical switch assembled in a passive alignment manner from a fiber array, a lens array and a movable mirror array produced by the MEMS technique.
In the general structure of the optical matrix switch, the collimator array and the micro-mirror array need to be fixed while positioned so that light beams of all channels emitted from the collimator array can be made accurately incident on corresponding micro-mirrors of the micro-mirror array respectively in order to achieve low-loss optical coupling.
In the conventional configuration of the optical switch, the lens array and the movable mirror array need to be disposed in postures oblique to each other and kept separate from each other so that the lens array does not interfere with beams reflected on the mirrors. It is conceived that beams emitted from the lens array have certain degrees of independent angular deviations respectively. For this reason, as the lens-mirror distance increases, the demand for higher fabrication accuracy of the lens array and higher positioning accuracy of the lens array and the movable mirror array increases in order to make all beams incident on the mirrors accurately. Moreover, the lens array and the movable mirror array are disposed so as to be oblique to each other. Accordingly, for example, passive alignment holes formed in the movable mirror array need to be fabricated obliquely. For this reason, the demand for higher angular accuracy of the holes and higher relative angular accuracy of surfaces of the passive alignment holding components in contact with the lens array and the movable mirror array increases. Accordingly, it is conceived that high positioning accuracy and high stability after fixing can be hardly obtained.